Lily's car has a fuel efficiency of $8$ liters per $100$ kilometers. What is the fuel efficiency of Lily's car in kilometers per liter?
Solution: Note that we need to reverse the independent and dependent variables for this ratio and that we want a unit rate. Since Lily's car has a fuel efficiency of $8$ liters per $100$ kilometers, we can likewise say it has a fuel efficiency of $100\,\text{km}$ per $8\,\text{L}$. $\begin{aligned} &\phantom{=}\dfrac{100\text{ km}}{8\text{ L}} \\\\ &= 12.5\,\dfrac{\text{km}}{\text{L}} \end{aligned}$ In conclusion, the fuel efficiency of Lily's car in $\dfrac{\text{km}}{\text{L}}$ is: $12.5\,\dfrac{\text{km}}{\text{L}}$